Method and apparatus for controlling radiation beam intensity directed to microlithographic substrates

ABSTRACT

A method and apparatus for controlling an intensity distribution of a radiation beam directed to a microlithographic substrate. The method can include directing a radiation beam from a radiation source along the radiation path, with the radiation beam having a first distribution of intensity as the function of location in a plane generally transverse to the radiation path. The radiation beam impinges on an adaptive structure positioned in the radiation path and an intensity distribution of the radiation beam is changed from the first distribution to a second distribution by changing a state of the first portion of the adaptive structure relative to a second portion of the adaptive structure. For example, the transmissivity of the first portion, or inclination of the first portion can be changed relative to the second portion. The radiation is then directed away from the adaptive structure to impinge on the microlithographic substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 10/870,561, filed Jun. 16, 2004, now U.S. Pat. No.7,046,340, issued May 16, 2006, which is a divisional application ofU.S. patent application Ser. No. 09/945,316, entitled “METHOD ANDAPPARATUS FOR CONTROLLING RADIATION BEAM INTENSITY DIRECTED TOMICROLITHOGRAPHIC SUBSTRATES,” filed Aug. 30, 2001, now U.S. Pat. No.6,794,100, issued Sep. 21, 2004, both of which are incorporated hereinin their entireties by reference. This application also relates tomaterial disclosed in U.S. patent application Ser. No. 09/945,467entitled “METHOD AND APPARATUS FOR IRRADIATING A MICROLITHOGRAPHICSUBSTRATE,” filed on Aug. 30, 2001, now U.S. Pat. No. 6,784,975, issuedAug. 31, 2004, and incorporated herein in its entirety by reference.

BACKGROUND

The present invention is directed toward methods and apparatuses forcontrolling the intensity of a radiation beam directed toward amicrolithographic substrate. Microelectronic features are typicallyformed in microelectronic substrates (such as semiconductor wafers) byselectively removing material from the wafer and filling in theresulting openings with insulative, semiconductive, or conductivematerials. One typical process includes depositing a layer ofradiation-sensitive photoresist material on the wafer, then positioninga patterned mask or reticle over the photoresist layer, and thenexposing the masked photoresist layer to a selected radiation. The waferis then exposed to a developer, such as an aqueous base or a solvent. Inone case, the photoresist layer is initially generally soluble in thedeveloper, and the portions of the photoresist layer exposed to theradiation through patterned openings in the mask change from beinggenerally soluble to become generally resistant to the developer (e.g.,so as to have low solubility). Alternatively, the photoresist layer canbe initially generally insoluble in the developer, and the portions ofthe photoresist layer exposed to the radiation through the openings inthe mask become more soluble. In either case, the portions of thephotoresist layer that are resistant to the developer remain on thewafer, and the rest of the photoresist layer is removed by the developerto expose the wafer material below.

The wafer is then subjected to etching or metal disposition processes.In an etching process, the etchant removes exposed material, but notmaterial protected beneath the remaining portions of the photoresistlayer. Accordingly, the etchant creates a pattern of openings (such asgrooves, channels, or holes) in the wafer material or in materialsdeposited on the wafer. These openings can be filled with insulative,conductive, or semiconductive materials to build layers ofmicroelectronic features on the wafer. The wafer is then singulated toform individual chips, which can be incorporated into a wide variety ofelectronic products, such as computers and other consumer or industrialelectronic devices.

As the size of the microelectronic features formed in the waferdecreases (for example, to reduce the size of the chips placed inelectronic devices), the size of the features formed in the photoresistlayer must also decrease. In some processes, the dimensions (referred toas critical dimensions) of selected features are evaluated as adiagnostic measure to determine whether the dimensions of other featurescomply with manufacturing specifications. Critical dimensions areaccordingly selected to be the most likely to suffer from errorsresulting from any of a number of aspects of the foregoing process. Sucherrors can include errors generated by the radiation source and/or theoptics between the radiation source and the mask. The errors can also begenerated by the mask, by differences between masks, and/or by errors inthe etch process. The critical dimensions can also be affected by errorsin processes occurring prior to or during the exposure/developmentprocess, and/or subsequent to the etching process, such as variations indeposition processes, and/or variations in material removal processes,such as chemical-mechanical planarization processes.

One general approach to correcting lens aberrations in wafer opticsystems (disclosed in U.S. Pat. No. 5,142,132 to McDonald et al.) is toreflect the incident radiation from a deformable mirror, which can beadjusted to correct for the aberrations in the lens optics. However,correcting lens aberrations will not generally be adequate to addressthe additional factors (described above) that can adversely affectcritical dimensions. Accordingly, another approach to addressing some ofthe foregoing variations and errors is to interpose a gradient filterbetween the radiation source and the mask to spatially adjust theintensity of the radiation striking the wafer. Alternatively, a thinfilm or pellicle can be disposed over the mask to alter the intensity oflight transmitted through the mask. In either case, the filter and/orthe pellicle can account for variations between masks by decreasing theradiation intensity incident on one portion of the mask relative to theradiation intensity incident on another.

One drawback with the foregoing arrangement is that it may be difficultand/or time-consuming to change the gradient filter and/or the pelliclewhen the mask is changed. A further drawback is that the gradient filterand the pellicle cannot account for new errors and/or changes in theerrors introduced into the system as the system ages or otherwisechanges.

SUMMARY

The present invention is directed to methods and apparatuses forcontrolling the intensity distribution of radiation directed tomicrolithographic substrates. In one aspect of the invention, the methodcan include directing a radiation beam from a radiation source alongradiation path, with the radiation beam having a first distribution ofintensity as a function of location in a plane generally transverse tothe radiation path. The method can further include impinging theradiation beam on an adaptive structure positioned in the radiationpath, and changing an intensity distribution of the radiation beam fromthe first distribution to a second distribution different than the firstdistribution by changing a state of a first portion of the adaptivestructure relative to a second portion of the adaptive structure. Themethod can further include directing the radiation beam away from theadaptive structure along the radiation path and impinging the radiationbeam directed away from the adaptive structure on the microlithographicsubstrate.

In a further aspect of the invention, the method can include impinging afirst portion of the radiation beam on a first portion of a reflectivemedium and impinging a second portion of the radiation beam on a secondportion of the reflective medium. The method can further include movingthe first portion of the reflective medium relative to the secondportion, and reflecting at least part of the first portion of theradiation beam toward a first portion of a grating having a firsttransmissivity, and reflecting at least part of the second portion ofthe radiation beam toward a second portion of the grating having asecond transmissivity greater than the first transmissivity. At leastpart of the second portion of the radiation beam then passes through thegrating to impinge on the microlithographic substrate, while at leastpart of the first portion of the radiation beam is attenuated or blockedfrom passing through the grating.

The invention is also directed toward an apparatus for controlling anintensity distribution of radiation directed to a microlithographicsubstrate. The apparatus can include a substrate support having asupport surface positioned to carry a microlithographic substrate, and asource of radiation positioned to direct a radiation beam along aradiation path toward the substrate support. The apparatus can furtherinclude an adaptive structure positioned in the radiation path andconfigured to receive the radiation beam with a first intensitydistribution and transmit the radiation beam with a second intensitydistribution different than the first intensity distribution. Theadaptive structure can have a first portion and a second portion, eachpositioned to receive the radiation and changeable from a first state toa second state, wherein the adaptive structure is configured to transmitthe radiation with the second intensity distribution when the firstportion is in the first state and the second portion is in the secondstate. The apparatus can further include a controller operativelycoupled to the adaptive structure to direct at least one of the firstand second portions to change from the first state to the second stateto change an intensity distribution of the radiation beam from the firstintensity distribution to the second intensity distribution.

In a further aspect of the invention, the adaptive structure can includea selectively transmissive medium having a first portion aligned with afirst portion of the radiation beam when the radiation beam is emittedfrom the radiation source, and a second portion aligned with the secondportion of the radiation beam. Each of the first and second portions canhave a transmissivity that is changeable from a first transmissivity toa second transmissivity different than the first transmissivity.Alternatively, the adaptive structure can include a reflective mediumhaving a first portion aligned with a first portion of the radiationbeam when the radiation beam is emitted from the radiation source, and asecond portion aligned with a second portion of the radiation beam. Eachof the first and second portions of the reflective medium can be coupledto at least one actuator to move from a first inclination angle relativeto the radiation path to a second inclination angle relative to theradiation path, with the second inclination angle being different thanthe first inclination angle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially schematic view of an apparatus for irradiatingmicrolithographic substrates in accordance with an embodiment of theinvention.

FIG. 2 is a partially schematic view of a portion of an adaptivestructure that includes a reflective medium and a diffuser plate inaccordance with an embodiment of the invention.

FIG. 3 is a partially schematic view of an adaptive structure thatincludes a reflective medium and a diffuser plate in accordance withanother embodiment of the invention.

FIG. 4 is a partially schematic view of an adaptive structure thatincludes a selectively transmissive medium in accordance with yetanother embodiment of the invention.

FIG. 5 is a flow chart illustrating a method for adjustingcharacteristics of radiation directed toward a microlithographicsubstrate in accordance with an embodiment of the invention.

FIGS. 6A–6C are flow diagrams illustrating details of methods foradjusting the radiation directed toward microlithographic substrates inaccordance with further embodiments of the invention.

DETAILED DESCRIPTION

The present disclosure describes methods and apparatuses for controllingthe intensity of radiation directed toward a microlithographicsubstrate. The term “microlithographic substrate” is used throughout toinclude substrates upon which and/or in which microelectronic circuitsor components, data storage elements or layers, vias or conductivelines, micro-optic features, micromechanical features, and/ormicrobiological features are or can be fabricated usingmicrolithographic techniques. Many specific details of certainembodiments of the invention are set forth in the following descriptionand in FIGS. 1–6C to provide a thorough understanding of theseembodiments. One skilled in the art, however, will understand that thepresent invention may have additional embodiments, and that theinvention may be practiced without several of the details describedbelow.

FIG. 1 schematically illustrates an apparatus 110 for controllablyirradiating a microlithographic substrate 160 in accordance with anembodiment of the invention. The apparatus 110 can include a radiationsource 120 that directs an electromagnetic radiation beam 128 along aradiation path 180 toward the microlithographic substrate 160. Theapparatus 110 can further include an adaptive structure 140 that adjuststhe intensity distribution of the incoming radiation beam 128.Optionally, the radiation beam 128 can then pass through a lens system123 configured to shape and/or magnify the radiation emitted by thesource 120. Optionally, the apparatus 110 can further include adiffractive element 122 to diffuse the radiation, and a light tube 124positioned to generate a plurality of images of the radiation source120. The light tube 124 and/or or a sizing lens 125 can size theradiation beam 128, which can then be directed by a mirror 126 through afocusing lens 127 to a reticle or mask 130 along a reticle radiationpath segment 181 a.

The reticle 130 can include reticle apertures 131 through which theradiation passes to form an image on the microlithographic substrate160. The radiation passes through a reduction lens 139 which reduces theimage pattern defined by the reticle to a size corresponding to the sizeof the features to be formed on the microlithographic substrate 160. Theradiation beam 128 then travels in a second direction 182 along asubstrate radiation path segment 182 a, and impinges on aradiation-sensitive material (such as a photoresist layer 161) of themicrolithographic substrate 160 to form an image on the layer 161. Inone embodiment, the beam 128 impinging on the layer 161 can have agenerally rectangular shape with a width of from about 5 mm. to about 8mm. and a length of about 26 mm. In other embodiments, the beam 128incident on the layer 161 can have other shapes and sizes. In oneembodiment, the radiation can have a wavelength in the range of about157 nanometers or less (for example, 13 nanometers) to a value of about365 nanometers or more. For example, the radiation can have a wavelengthof about 193 nanometers. In other embodiments, the radiation can haveother wavelengths suitable for exposing the layer 161 on themicrolithographic substrate 160.

The microlithographic substrate 160 is supported on a substrate support150. In one embodiment (a scanner arrangement), the substrate support150 moves along a substrate support path 151, and the reticle 130 movesin the opposite direction along a reticle path 132 to scan the imageproduced by the reticle 130 across the layer 161 while the position ofthe radiation beam 128 remains fixed. Accordingly, the substrate support150 can be coupled to a support actuator 154 and the reticle 130 can becoupled to a reticle actuator 137.

As the reticle 130 moves opposite the microlithographic substrate 160,the radiation source 120 can flash to irradiate successive portions ofthe microlithographic substrate 160 with corresponding successive imagesproduced by the reticle 130, until an entire field of themicrolithographic substrate 160 is scanned. In one embodiment, theradiation source 120 can flash at a rate of about 20 cycles during thetime required for the microlithographic substrate 160 to move by onebeam width (e.g., by from about 5 mm. to about 8 mm.). In otherembodiments, the radiation source 120 can flash at other rates. In anyof these embodiments, the radiation source 120 can flash at the samerate throughout the scanning process (assuming the reticle 130 and thesubstrate 150 each move at a constant rate) to uniformly irradiate eachfield. Alternatively, the radiation source 120 can deliver a continuousradiation beam 128. In either embodiment, each field can include one ormore dice or chips, and in other embodiments, each field can includeother features.

In another embodiment (a stepper arrangement), the radiation beam 128and the reticle 130 can expose an entire field of the microlithographicsubstrate 160 in one or more flashes, while the reticle 130 and thesubstrate support 150 remain in a fixed transverse position relative tothe radiation path 180. After the field has been exposed, the reticle130 and/or substrate support 150 can be moved transverse to theradiation path 180 to align other fields with the radiation beam 128.This process can be repeated until each of the fields of themicrolithographic substrate 160 is exposed to the radiation beam 128.Suitable scanner and stepper devices are available from ASML ofVeldhoven, The Netherlands; Canon USA, Inc., of Lake Success, N.Y.; andNikon, Inc. of Tokyo, Japan.

In a further aspect of this embodiment, a controller 170 is operativelycoupled to the reticle 130 (or the reticle actuator 137) and thesubstrate support 150 (or the support actuator 154). Accordingly, thecontroller 170 can include a processor, microprocessor or other devicethat can automatically (with or without user input) control andcoordinate the relative movement between these elements. The controller170 can also be coupled to the adaptive structure 140 to control theintensity distribution of the radiation beam 128, as described ingreater detail below.

FIG. 2 is a schematic view of the adaptive structure 140 described abovewith reference to FIG. 1 in accordance with an embodiment of theinvention. In one aspect of this embodiment, the adaptive structure 140can include a reflective medium 141, a grating 144, and a diffuser 148,all positioned along the radiation path 180. The reflective medium 141can include a two-dimensional array of movable reflective elements 142(four of which are shown schematically in FIG. 2 as elements 142 a–d),coupled to a corresponding plurality of actuators 143 (shown asactuators 143 a–d). For example, the reflective medium 141 can include adigital multi-mirror device, such as a device available from TexasInstruments of Dallas, Tex. Accordingly, each reflective element 142 canform a portion of a larger reflective surface 149 and can moveindependently of the other reflective elements. The interstices betweenthe reflective elements 146 can be filled with a reflective (oroptionally, a non-reflective) material that allows for relative movementof adjacent elements 142.

The reflective elements 142 direct the radiation beam 128 to the grating144. In one embodiment, the grating 144 can include first portions orregions 145 (shown as first regions 145-a–d) positioned between secondportions or regions 146 (shown as second regions 146 a–d). In oneembodiment, the first regions 145 can be opaque and the second regions146 can be transparent. In other embodiments, the first and secondregions 145, 146 can have other transmissivities for which a firsttransmissivity of the first regions 145 is less than a secondtransmissivity of the second regions 146. In one embodiment, the firstregions 145 can be formed by a rectilinear grid of lines disposed on anotherwise transparent (or at least more transmissive) substrate, such asquartz. In other embodiments, the first regions 145 can have othershapes and arrangements. In any of these embodiments, the first regions145 can intersect some of the radiation directed by the reflectivemedium 141 toward the grating 144 to locally reduce the intensity of theradiation passing through the grating 144. In a further aspect of thisembodiment, the first regions 145 can have an absorptive coating 147facing toward the reflective medium 141 to prevent the intersectedradiation from reflecting back toward the reflective medium 141.

The diffuser 148 receives the radiation passing through the grating 144and smooths what might otherwise be discrete shadows or discontinuitiesin the intensity distribution produced by the first regions 145 of thegrating 144. Accordingly, the diffuser 148 can produce an intensitydistribution represented schematically in FIG. 2 by line 182 anddescribed in greater detail below.

In operation, each of the reflective elements 142 of the reflectivemedium 141 can be positioned to direct portions of the impingingradiation beam 128 (which has an initial, generally uniform intensitydistribution across the section of the beam) in a selected manner toproduce a different intensity distribution. For example, element 142 bcan be positioned to direct a radiation beamlet 128 b directly betweentwo first regions 145 b and 145 c to produce an undeflected level ofintensity, as indicated by line 182. Elements 142 c and 142 d can bepositioned to direct radiation beamlets 128 c and 128 d, respectively,directly toward first region 145 d. Accordingly, the radiation reflectedby these elements will have a reduced intensity, as is also shown byline 182. The reflective element 142 a can be positioned to direct aradiation beamlet 128 a that illuminates less than the entirecorresponding first region 145 a to produce a level of intensity that isless than that produced by element 142 b, but greater than that producedby elements 142 c and 142 d. Similar adjustments can be made to theentire array of reflective elements 142 to selectively tailor theintensity distribution to a selected level.

In one embodiment, the resolution of the changes in intensitydistribution shown in FIG. 2 can be relatively coarse in comparison tothe individual features produced on the microlithographic substrate 160(FIG. 1). For example, the microelectronic or other microlithographicfeatures formed in the microlithographic substrate 160 can havedimensions on the order of less than one micron, while the distancebetween adjacent portions of the radiation beam 128 having differentintensities can be from about 0.3 mm. to about 1 mm. or greater. In oneembodiment, the shift in intensity can be less than about 10% of theundeflected intensity of the radiation beam 128 (e.g., less than about10% of the intensity incident on the reflective medium 141). In otherembodiments, the maximum deviation in intensity from any portion of theradiation beam 128 to any other portion can be less than about 5% of theincident intensity, and in a specific embodiment, can be from about 1%to about 2% of the incident intensity. Accordingly, the grating 144 canhave an open area of about 90 percent in one embodiment, and can have agreater open area in other embodiments.

FIG. 3 is a partially schematic illustration of another embodiment ofthe adaptive structure 140 described above with reference to FIG. 2. Inone aspect of this embodiment, the adaptive structure 140 does notinclude a grating 144. Accordingly, the reflective elements 142 a–d candirect corresponding radiation beamlets 128 a–d at different anglesdirectly to the diffuser 148. The diffuser 148 can smooth outtransitions between regions of the radiation beam 128 having differentintensities (generally as described above) to produce a radiationdistribution line 382. In one aspect of this embodiment, the radiationbeamlets 128 c and 128 d can combine to produce a local intensitygreater than the undeflected intensity. One advantage of the arrangementshown in FIG. 3 when compared to the arrangement shown in FIG. 2 is thatthe overall intensity of the radiation beam shown in FIG. 3 can begreater than that shown in FIG. 2 because the grating 144 (which canabsorb a portion of the radiation) is eliminated. Conversely, anadvantage of the arrangement shown in FIG. 2 is that the grating 144 canprovide an added degree of control over the reflected radiation beam 128(for example, it may dampen the effect of system vibrations), whencompared to an arrangement that includes the diffuser 148 alone.

FIG. 4 is a partially schematic illustration of an adaptive structure440 having a mirror 483 that directs the radiation beam 128 to impingeon a variably transmissive medium 480. The variably transmissive medium480 can include a liquid crystal material arranged to form variablytransmissive elements 481 (shown in FIG. 4 as elements 481 a–c). Thevariably transmissive elements 481 can be coupled to a source ofelectrical power and can be reversibly changed from one transmissivestate to another, within a range of transmissivities that can vary fromtransparent or nearly transparent to opaque or nearly opaque. Forexample, the variably transmissive elements 481 a can be selected to betransparent or at least approximately transparent to pass a portion ofthe radiation beam 128 through the variably transmissive medium 480 at ahigh level of intensity, as shown by intensity line 482. The variablytransmissive elements 481 b can have a lower transmissivity to reducethe intensity of a corresponding portion of the radiation beam 128. Thevariably transmissive elements 481 c can have a transmissivity lowerthan that of the elements 481 b to further reduce the intensity of acorresponding portion of the radiation beam 128. In other embodiments,the states of the variably transmissive elements 481 can be changed inother manners to produce any of a wide variety of intensitydistributions in the radiation beam 128.

In other embodiments, the adaptive structure 440 can have otherarrangements. For example, the variably transmissive medium 480 caninclude materials other than a liquid crystal material. In anotheralternate embodiment, the variably transmissive medium can include asingle, continuously variable element in place of the plurality ofelements described above. In any of the foregoing embodiments, theadaptive structure 440 can adjust the intensity of the radiation beam tothe levels and resolutions described above with reference to FIG. 2.

FIG. 5 is a flow diagram illustrating steps of a method for using any ofthe apparatuses described above with reference to FIGS. 1–4 inaccordance with an embodiment of the invention. FIGS. 6A–6C illustratefurther details of the steps shown in FIG. 5. Beginning with FIG. 5, amethod 500 can include irradiating a microlithographic substrate with aradiation beam having a selected intensity distribution to form an imageon the microlithographic substrate (step 502). The method can furtherinclude forming features in the microlithographic substrate based on theimage formed in step 502 (step 504). In step 506, characteristics of thefeatures formed in the microlithographic substrate are compared withtarget characteristics. In step 508, the process includes determiningwhether the characteristics of the features are within pre-selectedlimits. If the characteristics are within the limits, the process ends.If not, the configuration or setting of the adaptive structure isadjusted in step 510, and the process is repeated with a differentmicrolithographic substrate.

FIG. 6A illustrates details of an embodiment of the process for formingfeatures in the microlithographic substrate based on the image formedwith the radiation beam (step 504). In one aspect of this embodiment,the process can further include developing the image in a photoresistlayer (step 602). The material beneath the photoresist layer can beselectively etched to form recesses (step 604). The recesses can befilled with a conductive, semiconductive, or non-conductive material(step 606). Once the recesses have been filled, excess material can beremoved from the microlithographic substrate, for example, bychemical-mechanical planarization, in step 608.

FIG. 6B illustrates further details of embodiments of the process forcomparing characteristics of features in the microlithographic substratewith target characteristics (step 506). In step 610, the process caninclude selecting the features of the microlithographic substrate. Forexample, the features can include control structures specifically formedin the microlithographic substrate for diagnostic purposes.Alternatively, the process can include selecting other structures of themicrolithographic substrate, such as features configured to be operatedby the end user. In still a further embodiment, the features can includefeatures formed in a photoresist layer prior to etching or depositingmaterials on the microlithographic substrate. In any of theseembodiments, the process can include comparing measured featuredimensions with target values for the same dimensions (step 612). In aspecific aspect of this process, the method can include analyzing thefeatures with an electron microscope and comparing the measured resultswith target results. In another embodiment (step 614), the method caninclude comparing the conductivity of one or more features with a targetconductivity. In any of the foregoing embodiments, the process ofcomparing characteristics of microelectronic or other microlithographicfeatures with target characteristics can be repeated until an entire dieis checked (step 616) and/or until an entire field and/or wafer ischecked (step 618). The process can also be carried out on a pluralityof wafers or other microlithographic substrates.

FIG. 6C illustrates details of an embodiment of the process of adjustingthe setting of the adaptive structure (step 510). For example, when theadaptive structure includes tiltable or otherwise moveable reflectiveelements, the process can include adjusting the inclination angle of thereflective elements relative to the radiation path (step 620).Alternatively, for example, when the adaptive structure includesvariably transmissive elements, the process can include adjusting thetransmissivity of selected transmissive elements (step 622). In eitherembodiment, the process can further include replacing an initialmicrolithographic substrate with a subsequent microlithographicsubstrate after the adjustment (step 624), for example, to determine theeffect of the adjustment.

One feature of the arrangements described above with reference to FIGS.1–6C is that the adaptive structures can be easily altered by providinginstructions from the controller 170. An advantage of this feature isthat unlike conventional filters and pellicles, the structure thattailors the intensity of the radiation need not be removed from thesystem and replaced in order to produce a new intensity distribution.Accordingly, this arrangement can be less expensive than conventionalarrangements because it requires fewer pieces of hardware. Thearrangement can also be more efficient than conventional arrangementsbecause it can take less time to change the intensity distribution ofthe radiation beam.

Another advantage of the arrangements described above with reference toFIG. 1–6C is that they can be used to account for a wide range offactors that can systematically cause characteristics of themicroelectronic or other microlithographic features to deviate fromtheir target characteristics. For example, the adaptive structure can beadjusted to account for slight variations across a given mask and/orbetween different masks or reticles that are configured to produce thesame illumination pattern on one or more microlithographic substrates,but that may fail to do so due to manufacturing tolerances or errors.Alternatively, the adaptive structure can be used to account for thedegradation that can occur to a single mask and/or other system opticsand/or the radiation source over the course of time. Still further, theadaptive structure can tailor the intensity distribution of the incidentradiation beam to correspond to a variety of different masks having awide variety of disparate aperture patterns. For example, the adaptivestructure can have a first configuration when used with a first mask toform one type of microelectronic die or chip, and can be changed to asecond configuration when used with a second mask to form a differenttype of microelectronic die or chip.

In other embodiments, the adaptive structure can be used to account forvariations produced by other aspects of the process or processes forforming microelectronic devices or other microlithographic features. Forexample, if a particular section of the microlithographic substrate ormicrolithographic substrate field tends to etch more slowly than another(producing features that are undersized), the intensity of the radiationdirected to this region can be increased. The increased radiation canlocally increase the radiation dose and therefore the size of thefeatures formed in that region. If one region of the microlithographicsubstrate has a non-uniform optical thickness as a result of priormaterial deposition and/or removal processes (such as CMP processes),this can alter the manner in which the radiation-sensitive materialsubsequently disposed on the microlithographic substrate behaves. Forexample, optically non-uniform regions may reflect incident radiationdifferently than uniform regions, which can change the amount ofreflected radiation absorbed by the photoresist layer on themicrolithographic substrate. The intensity distribution of the radiationdirected toward this portion of the substrate can be altered to accountfor this non-uniformity, for example by increasing the incidentradiation intensity where the radiation absorption is less than a targetlevel, and/or decreasing the incident radiation intensity where theradiation absorption is greater than a target level.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from thespirit and scope of the invention. For example, in one embodiment, theapparatus can include both a deformable reflective medium and a variablytransmissive medium to increase the degree of control over the intensityof the radiation exiting the adaptive structure. In another embodiment,any of the refractive elements described above, including the reticle,can be replaced with reflective elements that perform generally the samefunction. Accordingly, the invention is not limited except as by theappended claims.

1. A method for processing a microelectronic substrate, the methodcomprising: directing a radiation beam from a radiation source along aradiation path to an adaptive structure, the radiation beam having afirst generally uniform distribution of intensity as a function oflocation in a plane generally transverse to the radiation path; changingan intensity distribution of the radiation beam from the firstdistribution to a second distribution different than the firstdistribution by changing a reflection angle of a first portion of theadaptive structure relative to a reflection angle of a second portion ofthe adaptive structure; directing the radiation beam away from theadaptive structure and through a reticle positioned between the adaptivestructure and the microelectronic substrate; and impinging the radiationbeam on the microelectronic substrate.
 2. The method of claim 1 whereinthe adaptive structure includes a reflective surface having a firstportion coupled to a first actuator and a second portion coupled to asecond actuator, and wherein: directing a radiation beam from aradiation source along a radiation path to an adaptive structurecomprises impinging a first portion of the radiation beam on the firstportion of the reflective surface and impinging a second portion of theradiation beam on the second portion of the reflective surface; andchanging a reflection angle of a first portion of the adaptive structurerelative to a reflection angle of a second portion of the adaptivestructure comprises moving the first portion of the reflective surfacerelative to the second portion of the reflective surface.
 3. The methodof claim 2, further comprising: reflecting at least part of the firstportion of the radiation beam toward a first portion of a grating havinga first transmissivity and reflecting at least part of the secondportion of the radiation beam toward a second portion of the gratinghaving a second transmissivity greater than the first transmissivity;and passing at least part of the second portion of the radiation beamthrough the grating to impinge on the microelectronic substrate.
 4. Themethod of claim 1 wherein impinging the radiation beam on themicroelectronic substrate includes impinging the radiation beam on aradiation-sensitive layer of the microelectronic substrate.
 5. Themethod of claim 1 wherein impinging the radiation beam on themicroelectronic substrate includes impinging the radiation beam on aphotoresist layer of the microelectronic substrate.
 6. The method ofclaim 1 wherein directing the radiation beam away from the adaptivestructure and through a reticle comprises passing the radiation beamthrough a reticle to form an image on the microelectronic substrate, andwherein the method further comprises: scanning the reticle and themicroelectronic substrate relative to each other by moving the reticlealong a reticle path generally normal to the radiation path proximate tothe reticle and moving the microelectronic substrate along a substratepath in a direction opposite the reticle and generally normal to theradiation path.
 7. The method of claim 1 wherein directing the radiationbeam away from the adaptive structure and through a reticle comprisespassing the radiation beam through a reticle to form an image on themicroelectronic substrate, and wherein the method further comprises:stepping the microelectronic substrate and the reticle relative to eachother by impinging the radiation on a first field of the microelectronicsubstrate while the microelectronic substrate is in a first fixedtransverse alignment relative to the reticle, moving at least one of thereticle and the microelectronic substrate transversely relative to theother to align a second field with the reticle, and exposing the secondfield to the radiation while the microelectronic substrate is in asecond fixed transverse alignment relative to the reticle.
 8. The methodof claim 1 wherein changing an intensity distribution of the radiationbeam from the first distribution to the second distribution compriseschanging each portion of the second distribution by no more than aboutten percent relative to the corresponding portion of the firstdistribution.
 9. The method of claim 1 wherein changing an intensitydistribution of the radiation beam from the first distribution to thesecond distribution comprises changing each portion of the seconddistribution by no more than about five percent relative to thecorresponding portion of the first distribution.
 10. The method of claim1 wherein impinging the radiation beam on the microelectronic substrateincludes irradiating a first portion of the microelectronic substratewith radiation at a first intensity and irradiating a second portion ofthe microelectronic substrate with radiation at a second intensity, thesecond portion of the microelectronic substrate being spaced apart fromthe first portion of the microelectronic substrate by a distance ofabout 0.3 millimeters or greater.
 11. The method of claim 1 wherein theradiation beam has an average intensity after being directed away fromthe adaptive structure, and wherein impinging the radiation beam on themicroelectronic substrate includes impinging radiation with a higherthan average intensity on a first field of the microelectronic substrateand impinging radiation with a lower than average intensity on a secondfield of the microelectronic substrate.
 12. The method of claim 1wherein the radiation beam has an average intensity after being directedaway from the adaptive structure, and wherein impinging the radiationbeam on the microelectronic substrate includes impinging radiation witha higher than average intensity on a first microelectronic die of themicroelectronic substrate and impinging radiation with a lower thanaverage intensity on a second microelectronic die of the microelectronicsubstrate.
 13. The method of claim 1, further comprising changing ashape of the radiation beam after impinging the radiation beam on theadaptive structure.
 14. The method of claim 1 wherein themicroelectronic substrate is a first microelectronic substrate having alayer of radiation-sensitive material, and wherein directing theradiation beam away from the adaptive structure and through a reticlecomprises passing the radiation beam through a reticle to form an imageon the microelectronic substrate, and wherein the method furthercomprises: forming features in the first microelectronic substrate basedon the image formed on the radiation sensitive material; determiningcharacteristics of the features formed in the first microelectronicsubstrate; based on the determined characteristics, changing anintensity distribution of the radiation beam from the first distributionto a third distribution different than the first and seconddistributions by changing a reflection angle of at least one of thefirst and second portions of the adaptive structure; and impinging theradiation beam with the third intensity distribution on a secondmicroelectronic substrate.
 15. A method for directing radiation toward amicroelectronic substrate, the method comprising: directing a radiationbeam along a radiation path to a reflective medium, a first portion ofthe radiation beam being impinged on a first portion of a reflectivemedium and a second portion of the radiation beam being impinged on asecond portion of the reflective medium; moving the first portion of thereflective medium relative to the second portion of the reflectivemedium to (a) direct the first portion of the radiation beam at a firstangle relative to the radiation path to a first portion of a selectivelytransmissive medium, and (b) direct the second portion of the radiationbeam at a second angle relative to the radiation path to a secondportion of the selectively transmissive medium, wherein each of thefirst and second portions of the selectively transmissive medium have atransmissivity that is changeable from a first transmissivity to asecond transmissivity different than the first transmissivity, at leastone of the first and second portions being configured to change from thefirst transmissivity to the second transmissivity without becomingopaque; and directing at least part of one of the first and secondportions of the radiation beam through the selectively transmissivemedium to impinge on the microelectronic substrate, while at leastinhibiting passage of at least part of the other of the first and secondportions of the radiation beam through the selectively transmissivemedium.
 16. The method of claim 15 wherein the radiation beam has afirst intensity distribution in a plane generally normal to theradiation path before impinging upon the reflective medium, and whereinthe method further comprises changing an intensity distribution of theradiation beam directed through the selectively transmissive medium fromthe first intensity distribution to a second intensity distributiondifferent than the first intensity distribution.
 17. The method of 16,further comprising smoothing the second intensity distribution bypassing the radiation beam through a diffuser after directing theradiation beam through the selectively transmissive medium and beforeimpinging the radiation beam on the microelectronic substrate.
 18. Themethod of claim 15, further comprising passing the radiation beamthrough a reticle after directing at least part of one of the first andsecond portions of the radiation beam through the selectivelytransmissive medium and before impinging the radiation beam on themicroelectronic substrate.
 19. The method of claim 15 wherein themicroelectronic substrate has a layer of radiation-sensitive materialand wherein directing at least part of one of the first and secondportions of the radiation beam through the selectively transmissivemedium to impinge on the microelectronic substrate includes impingingthe radiation beam on the radiation-sensitive material.
 20. The methodof claim 15, further comprising selecting the radiation beam to have awavelength of about 365 nanometers or less.
 21. The method of claim 15wherein the selectively transmissive medium comprises a grating, andwherein: directing the first and second portions of the radiation beamto corresponding first and second portions of the selectivelytransmissive medium comprises (a) directing the first portion of theradiation beam to a first portion of the grating having a firsttransmissivity, and (b) directing the second portion of the radiationbeam to a second portion of the grating having a second transmissivitygreater than the first transmissivity; and directing at least part ofthe second portion of the radiation beam through the selectivelytransmissive medium comprises directing at least part of the secondportion of the radiation beam through the second portion of the gratingwhile attenuating and/or blocking at least part of the first portion ofthe radiation beam from passing through the grating.
 22. The method ofclaim 21, further comprising selecting the grating to have an open areaof at least about 90 percent.
 23. The method of claim 15 wherein movingthe first portion of the reflective medium relative to the secondportion of the reflective medium comprises tilting a first reflectiveelement of the reflective medium relative to the radiation path to anangle different than an angle between the radiation path and a secondreflective element of the reflective medium.
 24. The method of claim 15wherein the selectively transmissive medium comprises a liquid crystalmaterial, and wherein the method further comprises changing a firstportion of the liquid crystal material to have a first transmissivitywithout making the first portion opaque and changing a second portion ofthe liquid crystal material to have a second transmissivity greater thanthe first portion before directing at least part of one of the first andsecond portions of the radiation beam through the liquid crystalmaterial.
 25. A method for directing a radiation beam from a radiationsource along a radiation path toward a microelectronic substrate, theradiation beam having a first distribution of intensity as a function oflocation in a plane generally transverse to the radiation path, themethod comprising: impinging a first portion of the radiation beam on afirst portion of a reflective medium and a second portion of theradiation beam on a second portion of the reflective medium; tilting thefirst portion of the reflective medium relative to the second portion ofthe reflective medium to change an intensity distribution of theradiation beam from the first distribution to a second distributiondifferent than the first distribution; reflecting at least part of thefirst portion of the radiation beam toward a first portion of a gratinghaving a first transmissivity and reflecting at least part of the secondportion of the radiation beam toward a second portion of the gratinghaving a second transmissivity greater than the first transmissivity;directing at least part of the second portion of the radiation beamthrough the grating to a reticle positioned between the selectivelytransmissive medium and the microelectronic substrate while attenuatingand/or blocking at least part of the first portion of the radiation beamfrom passing through the grating; and impinging the portion of theradiation beam passed through the grating and the reticle on themicroelectronic substrate.
 26. A method for processing a microelectronicsubstrate, the method comprising: directing a radiation beam from aradiation source along a radiation path to an adaptive structure, theradiation beam having a first distribution of intensity as a function oflocation in a plane generally transverse to the radiation path; changingan intensity distribution of the radiation beam from the firstdistribution to a second distribution different than the firstdistribution by changing a reflection angle of a first portion of theadaptive structure relative to a reflection angle of a second portion ofthe adaptive structure; directing the radiation beam away from theadaptive structure and through a reticle positioned between the adaptivestructure and the microelectronic substrate; and impinging the radiationbeam on the microelectronic substrate, wherein impinging the radiationbeam on the microelectronic substrate includes irradiating a firstportion of the microelectronic substrate with radiation at a firstintensity and irradiating a second portion of the microelectronicsubstrate with radiation at a second intensity, the second portion ofthe microelectronic substrate being spaced apart from the first portionof the microelectronic substrate by a distance of about 0.3 millimetersor greater.
 27. A method for processing microelectronic substrates, themethod comprising: directing a radiation beam from a radiation sourcealong a radiation path to an adaptive structure, the radiation beamhaving a first distribution of intensity as a function of location in aplane generally transverse to the radiation path; changing an intensitydistribution of the radiation beam from the first distribution to asecond distribution different than the first distribution by changing areflection angle of a first portion of the adaptive structure relativeto a reflection angle of a second portion of the adaptive structure;directing the radiation beam away from the adaptive structure andthrough a reticle positioned between the adaptive structure and themicroelectronic substrate; forming an image on a surface of a firstmicroelectronic substrate; forming features in the first microelectronicsubstrate based on the image; determining characteristics of thefeatures formed in the first microelectronic substrate; based on thedetermined characteristics, changing an intensity distribution of theradiation beam from the first distribution to a third distributiondifferent than the first and second distributions by changing areflection angle of at least one of the first and second portions of theadaptive structure; and impinging the radiation beam with the thirdintensity distribution on a second microelectronic substrate.